This application claims the priority of Application No. 102 312 22.2, filed Jul. 11, 2002, in Germany, the disclosure of which is expressly incorporated by reference herein.
The invention concerns a trailer coupling for motor vehicles with a coupling ball. The known trailer coupling also includes a drive motor by means of which the ball neck is reversibly movable with the coupling ball from a working position into a resting position. Such an arrangement is already known, for example, from EP 0 832 000 B1. With this arrangement, the control unit for the drive for moving the ball neck is blocked when the motor of the motor vehicle is running. Sensors, for example in the form of end position switches, are provided to record the working and resting position of the trailer coupling in any given case. A control unit ensures that either moving of the ball neck or travel of the motor vehicle is permitted. The control unit blocks the drive for the motion of the ball neck when the motor of the motor vehicle is running.
The object of the present invention is a further improvement of safety during activation of the trailer coupling.
This objective of the invention is accomplished with the characterizing features of the present invention whereby when one a plurality of predetermined conditions exist, the activation of the motion of the trailer pulling device is prevented.
It is especially advantageous that these different conditions are OR-linked. In this way, it is assured that in each case in which one of the defined conditions is not met, a motion of the trailer pulling device does not occur, resulting in the fact that once again the safety for bystanders is further increased.
Recording the rate of travel as one of these conditions has the advantage that two motions, the motion of the motor vehicle and the motion of the trailer pulling device, do not take place simultaneously, and the driver of the motor vehicle as well as well as bystanders do not need to pay attention to two processes at once. Moreover, the velocity v in the vehicle is already known for additional processes to be controlled, such as motor control, and needs only be read out by the control apparatus for activating the motion of the trailer-pulling device.
A verification of whether the trailer is coupled to the motor vehicle is simply possible in that the socket to the electrical connection of the trailer is monitored with a corresponding sensor able to recognize a trailer. A purely electronic recording is possible in which the direction of a travel indicator is briefly subjected to current in the shut off state and recognized through the rising voltage level of the trailer. It is guaranteed through such an evaluation that the trailer-pulling device is not actuated if a trailer is connected.
Checking whether the rear window or the tailgate is open is a condition that advantageously ensures that a person is situated in the direct swivel range of the trailer coupling.
In the final analysis, it is advantageous to monitor the motion of the trailer pulling device itself since this offers the possibility of stopping the motion of the trailer pulling device and/or reversing the direction of motion in the event resistance occurs, for example because a child has moved into the motion space of the trailer pulling device.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.